Hybrid Stars in the Light of GW170817

Nandi, Rana; Char, Prasanta

doi:10.3847/1538-4357/aab78c

Cited by 104 publications

(116 citation statements)

References 33 publications

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“…We observe that several of the stiffer reference equations of state, e.g. NL3, DDME2, and IOPB-I, lie outside the 90% confidence region, in keeping with the preference found by other studies [24,25,32,33] [29,30,57,58] or a universal chirpdeformability-radius relation [59]. It also overlaps with the result R 1.4 = 12.2 +1.0 −0.8 km obtained by Ref.…”

Section: A General Constraintssupporting

confidence: 91%

Inferring neutron star properties from GW170817 with universal relations

Kumar

Landry

2019

Phys. Rev. D

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Because all neutron stars share a common equation of state, tidal deformability constraints from the compact binary coalescence GW170817 have implications for the properties of neutron stars in other systems. Using equation-of-state insensitive relations between macroscopic observables like moment of inertia (I), tidal deformability (Λ) and stellar compactness, we derive constraints on these properties as a function of neutron-star mass based on the LIGO-Virgo collaboration's canonical deformability measurement, Λ1.4 = 190 +390 −120 . Specific estimates of Λ, I, dimensionless spin χ, and stellar radius R for a few systems targeted by radio or X-ray studies are extracted from the general constraints. We also infer the canonical neutron-star radius as R1.4 = 10.9 +1.9 −1.5 km at 90% confidence. We further demonstrate how a gravitational-wave measurement of Λ1.4 can be combined with independent measurements of neutron-star radii to tighten constraints on the tidal deformability as a proxy for the equation of state. We find that GW170817 and existing observations of six thermonuclear bursters in low-mass X-ray binaries jointly imply Λ1.4 = 196 +92 −63 at the 90% confidence level.1 A different universal relation has been used elsewhere in conjunction with GW170817 to constrain the maximum mass of nonrotating neutron stars [26]. 2 In the remainder of the paper, quoted error bars refer to symmetric 90% confidence intervals about the median unless otherwise specified. 3 Note added: A Bayesian analysis of this kind-but focused on the stellar radius, rather than the tidal deformability-is presented in Ref.[45], which appeared shortly after completion of this paper.

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Section: A General Constraintssupporting

confidence: 91%

Inferring neutron star properties from GW170817 with universal relations

Kumar

Landry

2019

Phys. Rev. D

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“…In the case of single phase transition our discussion is complementary to those given in Refs. [6,7,[10][11][12][13][14][15] but we take into account the possibility of various hadronic envelopes.…”

Section: B Quark Matter Eosmentioning

confidence: 99%

“…One possibility is a deconfinement phase transition from bound hadronic states to liberated quark states. The effect of a strong first-order phase transition on tidal deformabilities of the neutron star in the context of GW170817 event has been explored by a number of * jiajieli@itp.uni-frankfurt.de † sedrakian@fias.uni-frankfurt.de ‡ alford@physics.wustl.edu groups [5][6][7][8][9][10][11][12][13][14][15] showing that the hadron-quark phase transition at low enough density, ρ 2-3ρ 0 , where ρ 0 is the nuclear saturation density, relaxes the tension between the inferred tidal deformabilities and those predicted by purely hadronic models without a phase transition. Of particular interest in this context is the emergence of twin stars, where purely nucleonic and hybrid stars have the same masses, but different radii [6].…”

Section: Introductionmentioning

confidence: 99%

Relativistic hybrid stars with sequential first-order phase transitions and heavy-baryon envelopes

Sedrakian

Alford

2020

Phys. Rev. D

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We compute the mass, radius and tidal deformability of stars containing phase transitions from hadronic to quark phase(s). These quantities are computed for three types of hadronic envelopes: purely nuclear, hyperonic, and ∆-resonance-hyperon admixed matter. We consider either a single first-order phase transition to a quark phase with a maximally stiff equation of state (EoS) or two sequential first-order phase transitions mimicking a transition from hadronic (H) to a quark matter phase followed by a second phase transition to another quark phase. Such a construct emulates the results of the computations of the EoS which include 2SC and CFL color superconducting phases at low and high density. We explore the parameter space which produces low mass twin and triplet configurations where equal mass stars have substantially different radii and tidal deformabilities. We demonstrate that while for purely hadronic stiff EoS the obtained maximum mass is inconsistent with the upper limit on this quantity placed by GW170817, the inclusion of the hyperonic and ∆-resonance degrees of freedom, as well as the deconfinement phase transition at sufficiently low density, produce configuration of stars consistent with this limit. The obtained hybrid star configurations are in the mass range relevant for the interpretation of the GW170817 event. We compare our results for the tidal deformability with the limits inferred from GW170817 showing that the onset of non-nucleonic phases, such as ∆-resonance-hyperon admixed phase or/and the quark phase(s) is favored by this data if the nuclear EoS is stiff. Also, we show that low-mass twins and especially triplets proliferate the number of combinations of possible types of star that can undergo a merger event, the maximal number being six in the case of triplets. The prospects for uncovering the first-order phase transition(s) to and in quark matter via measurements of tidal deformabilities in merger events are discussed.

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“…EoS at densities relevant for medium-mass NSs. Incidentally, the analyses of K + production[95][96][97] and π − /π + production ratio[98] in heavy-ion collisions provide evidence for a soft EoS at similar densities.Combining empirical relations between Λ 1.4 and R 1.4 (see Section III B 1) with the upper limits on the tidal deformability obtained from the analyses of the gravitational-wave signal by the LIGO-Virgo collaboration[1,11] and De et al[10], different constraints have been proposed for the radius of a 1.4 M NS (see, e.g., Refs [13,14,17,77,99,100]…”

mentioning

confidence: 99%

Role of the symmetry energy and the neutron-matter stiffness on the tidal deformability of a neutron star with unified equations of state

2019

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The role of the symmetry energy and the neutron-matter stiffness on the tidal deformability of a cold nonaccreted neutron star is studied using a set of unified equations of state. Based on the nuclear energy-density functional theory, these equations of state provide a thermodynamically consistent treatment of all regions of the star and were calculated using functionals that were precision fitted to experimental and theoretical nuclear data. Predictions are compared to constraints inferred from the recent detection of the gravitational-wave signal GW170817 from a binary neutron-star merger and from observations of the electromagnetic counterparts.

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Hybrid Stars in the Light of GW170817

Cited by 104 publications

References 33 publications

Inferring neutron star properties from GW170817 with universal relations

Inferring neutron star properties from GW170817 with universal relations

Relativistic hybrid stars with sequential first-order phase transitions and heavy-baryon envelopes

Role of the symmetry energy and the neutron-matter stiffness on the tidal deformability of a neutron star with unified equations of state

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